Abstract

Background: Robotic assisted (RA) spine surgery was developed to reduce the morbidity for misplaced thoracolumbar (TL) pedicle screws (PS) resulting in neurovascular injuries, dural fistulas, and/or visceral/other injuries. RA is gaining the attention of spine surgeons to optimize the placement of TL PSs, and to do this more safely/effectively versus utilizing stereotactic navigation alone, or predominantly free hand (FH) techniques. However, little attention is being focused on whether a significant number of these TL RA instrumented fusions are necessary.

Methods: RA spine surgery has been developed to improve the safety, efficacy, and accuracy of minimally invasive TL versus open FH PS placement.

Results: Theoretical benefits of RA spine surgery include; enhanced accuracy of screw placement, fewer complications, less radiation exposure, smaller incisions, to minimize blood loss, reduce infection rates, shorten operative times, reduce postoperative recovery periods, and shorten lengths of stay. Cons of RA include; increased cost, increased morbidity with steep learning curves, robotic failures of registration, more soft tissue injuries, lateral skiving of drill guides, displacement of robotic arms impacting accurate PS placement, higher reoperation rates, and potential loss of accuracy with motion versus FH techniques. Notably, insufficient attention has been focused on the necessity for performing many of these TL PS instrumented fusions in the first place.

Conclusion: RA spinal surgery is still in its infancy, and comparison of RA versus FH techniques for TL PS placement demonstrates several potential pros, but also multiple cons. Further, more attention must be focused on whether many of these TL PS instrumented procedures are even warranted.

Keywords: Complications, Free hand: Pedicle screw placement, Morbidity, Robotic spine surgery: Neuronavigational, Skiving, Unnecessary fusions, Unwarranted surgery

INTRODUCTION

Robotic assisted (RA) spinal surgery was developed to reduce the frequency of neurological, vascular, visceral, and other injuries resulting from thoracolumbar (TL) pedicle screw (PS) fusions.[ 6 ] By 2019, the United States Food and Drug Administration had already approved 7 spinal RA devices manufactured by 4 companies for placing TL PS.[ 8 ] Potential pros for RA TL PS placement included; enhanced screw location/accuracy (i.e. improved visualization, dexterity), reduced morbidity, less surgeon/staff radiation exposure, and shorter operative times amongst others.[ 6 - 8 , 10 - 15 ] However, cons also included; the increased cost of RA, screw skiving resulting in inaccurate screw placement, potential displacement of the robotic arm with patient motion, higher reoperation rates, and steep learning curves.[ 1 , 2 , 7 , 9 , 11 - 13 , 16 ] Here, we have compared the pros and cons for TL PS placement utilizing spinal RA versus predominantly free hand (FH) techniques. Additionally, we have raised the question as to why and whether a significant subset of these procedures should be performed in the first place.

HISTORY OF RA FOR SPINE SURGERY

In 2004, the FDA approved the first RA device for spinal surgery in the USA; Mazor Robotics Ltd. (Caesarea, Israel).[ 2 , 13 ] RA was developed to reduce the incidence of TL PR-related complications seen with FH techniques.[ 1 , 2 , 6 - 16 ] Fan et al. (2018) summarized the incidence of FH lumbar PS complications as ranging from 5% to 41%, while the range for misplaced thoracic screws varied from 3% to 55%.[ 6 ]

COMPARISON OF ACCURACY OF RA VERSUS FH TL PEDICLE SCREW PLACEMENT

Different studies compared the safety/efficacy and pros/ cons of RA versus FH transpedicular screw placement in the thoracic or lumbar spine.[ 6 , 10 , 11 , 12 , 15 ]

SUPERIORITY OF FH OVER RA PLACEMENT OF PS IN THE LUMBAR SPINE

In a prospective randomized single center study, Ringel et al. (2012) looked at the safety/efficacy of PS placement for one or two-level lumbar fusions utilizing RA versus FH techniques [ Table 1 ].[ 12 ] Postoperative CT studies used Grades A-E to document the accuracy of PS screw placement; Grade A: no cortical violation; Grade B < 2 mm breach all the way to Grade E: >/=- 6 mm pedicle violation. Of 298 PS placed in 60 patients (FH, 152; RA, 146), 90% of FH, versus a lower 85% of RA screws were optimally placed (i.e., defined as Grades A/B).

Table 1:

Reports of robotics-assisted spine surgery.

SUPERIORITY OF RA VERSUS FH TECHNIQUES FOR TL PEDICLE SCREW PLACEMENT

Several studies documented the superiority of TL PS placement using RA-based versus FH techniques [ Table 1 ].[ 6 , 7 , 9 , 10 ] In 2017, Joseph et al. considered RA for spine surgery to be in its infancy.[ 9 ] The Gertzbein and Robbins grading system revealed an overall 85–100% accuracy of screw placement (i.e. accuracy as determined by Grades A or B: Grade A-no pedicle breach, Grade B-minimal pedicle breach). In a meta-analysis of 10 articles (2011–2016) involving 597 patients, 12 cadavers and 2937 screws, Fan et al. (2018) demonstrated more accurate screw placement for RA versus FH techniques as confirmed on postoperative CT-studies (i.e. pedicle breach of ≤3 mm).[ 6 ] When Ghasem et al. (2018) reviewed 32 RA versus FH articles for TL PS instrumentation, the accuracy was at least comparable if not superior using the RA techniques.[ 7 ] Khan et al. (2019) retrospectively evaluated the accuracy for lumbar PS placement in 20 patients with/without degenerative spondylolisthesis using the Mazor X (Mazor Robotics Ltd, Caesarea, Israel) RA device, and employed the Grade I-IV scale (i.e. Grade I [no pedicle breach], to Grade IV [breach >4 mm]) [ Table 1 ].[ 10 ] They found that 74 (98.7%) of screws were optimally (Grade I) placed at 24 spinal levels, only one screw (1.3%) was Grade II (medial

MINIMAL LEARNING CURVE AND PROS FOR RA VERSUS FH TL PS PLACEMENT

Minimal learning curve for RA versus FH screw placement

Two studies clearly documented a minimal learning curve for accurately placing TL PS using RA spinal techniqus [ Table 1 ].[ 10 , 15 ] When Khan et al. (2019) performed lumbar PS placement in 20 patients using the Mazor X (Mazor Robotics Ltd, Caesarea, Israel) RA device, 74 (98.7%) screws were optimally placed (Grade I: no breach), only one screw (1.3%) was in Grade II (medial breach 10 ] Vardiman et al. (2020), using the minimally invasive RA CT-based Gertzbein and Robbins system found that 600 screws placed in the TL spine showed no/minimal breach (Grades A/B) in 98.7% of cases when they were placed by an experienced attending surgeon, and a 97.67% accuracy for the inexperienced resident’s RA spinal cases.[ 15 ] Further, only 9 screws (1.5% of 600) in Grade C required intraoperative repositioning (Grade C), while none were in Grade D.

Pros for RA versus TL PS Placement

Potential benefits for RA placement of TL PS included; greater safety/efficacy/accuracy of PS placement, reduced complications, the ability to adapt RA to intraoperative navigational techniques, less radiation exposure (i.e. to the patient, surgeon, and staff), shorter operative/postoperative recovery times, a shorter average length of stay, smaller incisions, reduced blood loss, and lower infection rates [ Table 1 ].[ 2 , 6 , 7 , 9 , 11 - 14 , 16 ] Further, future RA techniques could be applied to; the resection of spinal tumors, ablations, vertebroplasties, spinal deformity, bony decompressions, dural closures, and pre-planned osteotomies.[ 2 , 7 , 13 , 14 , 16 ]

Steep learning curves and cons for RA spinal surgery

Cons for RA spinal surgery included; steep learning curves, greater cost, and technique-related difficulties compromising surgical accuracy [ Table 1 ].[ 1 , 9 , 12 , 13 ] Ringel et al. (2012) found significant weaknesses in the robotic spinal system; “One of their main concerns was screw skiving”. They further stated: “It is possible that a cannula sliding off an angled bone surface could result in a most difficult-to-prevent lateral screw inaccuracy.”[ 12 ] Ringel, in their randomized controlled trial stated that RA screw placement was significantly less accurate (i.e. only 85% accurate) versus 93% for the FH technique.[ 12 ] Ten screws placed with RA required intraoperative revision versus only one patient in the FH control population. Further, surgical time for screw placement was significantly longer for RA (95 min) versus for FH (84 min). They also noted that RA could not yet be used to perform cervical surgery (i.e. no appropriate place to mount the bridge). They concluded that the FH technique for screw placement was still more accurate than for RA, that misplaced RA screws typically deviated laterally, and a major flaw of RA was the attachment of the robotic device to the spine. These factors “...(led) to screw malposition as well as slipping of the implantation cannula at the screw entrance point (i.e. skiving).” [ 12 ] In Joseph et al. (2017) review of 12 studies, they found additional failures regarding RA spine surgery; registration failure, soft-tissue hindrance, and lateral skiving of the drill guide.”[ 9 ] Crawford et al. added to these RA risks: “skiving of the tool on bone, displacement of the robotic arm, or patient movement.”[ 1 ]

TIMES FOR PREPARATION, SURGERY, AND RADIATION EXPOSURE WITH RA VERSUS FH

Comparable or shorter times for preparation, surgery, and radiation exposure using RA vs. FH techniques

When Ringel et al. (2012) evaluated 298 screws (FH 152, RA 146) placed in 60 patients, the preparation time, operating times, and intraoperative radiation exposure times were similar for both populations [ Table 1 ].[ 12 ] In 2019, Kochanski et al., after comparing RA versus Image-Guided Navigation for performing TL PS instrumentation in deformity/complex spine procedures, noted that both procedures reduced radiation exposure requirements.[ 11 ]

Longer times for preparation, surgery, and radiation exposure for RA vs. FH techniques

Several authors documented that RA spinal procedures required longer operative times, and higher doses/longer duration of radiation exposure versus FH techniques [ Table 1 ].[ 7 , 11 , 16 ] However, a learning curve effect was noted for RA surgery, wherein initially longer operations, longer radiation exposure times, and longer duration of operations decreased with experience. Additionally, Ghasem et al. cautioned that; “screw trajectories should be checked,” as “drilling pathways (were/could be) altered by soft tissue pressures, forceful surgical application, and bony surface skiving.”[ 7 ]

NEED TO RECONSIDER AND ACKNOWLEDGE HIGH RATE OF UNNECESSARY TL PS SPINE FUSIONS UTILIZING RA VERSUS FH TECHNIQUES

Future studies may better document that RA offers technological advantages over FH procedures for placing TL PS. Nevertheless, one should exercise better clinical judgment as to whether and when these procedures are warranted [ Table 2 ].[ 3 - 5 ] Here, we defined unnecessary surgery as operations recommended to patients by another surgeon for pain alone, without significant neurological deficits, or significantly abnormal X-ray, MR, or CT findings.[ 3 - 5 ] In 2011, Epstein found that 47 (17.2%) of 274 patients coming in for second opinions were scheduled for unnecessary spinal surgery; 21 (23.1%) of 91 were scheduled for unnecessary cervical procedures/fusions, and 26 (14.2%) of 183 for unnecessary single/ 2-5 level lumbar interbody fusions.[ 3 ] This 2011 review article also focused on the incidence of overly extensive spine operations being offered to patients age 65 and older.[ 4 ] Further, in 2013, out of 183 second opinions performed by Epstein over a 20 month period, 111 (60.7%) needed no surgery, 61 (33.3%) were told to have overly extensive and/or the wrong surgery, while just 11 (6%) were initially advised to have the right surgery.[ 5 ] A cursory review of such high rates of unnecessary and/or overly extensive spinal fusions should prompt some surgeons to reevaluate whether and when to offer RA versus FH TL PS instrumented fusions.

Table 2:

Summary of Epstein’s Articles on Unnecessary Spine Surgery.

CONCLUSION

RA spinal procedures are still in their infancy as confirmed by the continued controversy regarding the relative safety/ efficacy and pros/cons of RA versus FH techniques for TL PS placement/instrumentation [ Tables 1, 2 ].[ 1 - 16 ] Clearly, more attention needs to be focused on whether and when to utilize TL PS instrumented fusion procedures, and how to better analyze/determine if they are warranted.

Declaration of patient consent

Patient’s consent not required as there are no patients in this study.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

COMMENTARY 1

Training

The issue of what training is appropriate for RA surgery is an on-line course, a weekend course, incorporation of RA training within a spine fellowship, or the presence of the robotics representative for every case. Ideally, patients with significant polytrauma and multiple complex TL fractures will be treated in a tertiary care or trauma center. These tertiary centers are more likely to have a fellowship trained spine surgeon on staff, and a robot. This would allow for the volume needed to solve the problem of a steep learning curve, and enough familiarity with complex fractures, spinal biomechanics, and RA surgery to trouble shoot difficult cases such as highly unstable fractures which may move with patient positioning. The use of RA surgery could instill a false since of confidence in those surgeons who typically don’t do complex spine surgery to leave their comfort zone; this is concerning for the performance of inappropriate surgeries or unnecessarily long constructs.

Monitoring

Who monitors the accuracy of the robots-the surgeons, the robot representatives, or operating room personnel? Equipment that is moved for every case and potentially bumped multiple times is bound to lose accuracy over time. Accuracy should be checked between cases, not just when there is a miss or malfunction. From a medical-legal perspective, if the equipment is owned by the hospital, it would be their responsibility to ensure the equipment is checked unless a purchase agreement included a lifetime representative. It is also concerning in that any instrumentation can be used with a given robotic system. Or, on the other hand, does this force the surgeon to use the specific spinal instrumentation that is manufactured or distributed with the robot. This creates a situation of monopoly with the robot/instrumentation company, and risks having a surgeon use instrumentation that they are less familiar with which can increase the incidence of inadvertent mistakes, and additional OR time.

Costs

Does the potential accuracy of thoracic screw placement replace the need for intraoperative monitoring, or just add an additional cost of increased OR time and disposables? Does bundling of the robot and the spinal instrumentation increase the price of the spinal instrumentation in efforts to decrease the cost of the robot? Will RA be demanded by patients for all lumbar cases since it is a potential marketing tool? All these factors must be accounted for when determining the value and effiaccy in spinal surgery, otherwise we are driving costs up without added benefit.

Prof. Jamie Baisden MD

MCW-Neurosurgery

HUB 4th Floor

8701 Watertown Plank Rd

Milwaukee, WI 53226

Cell 262 902 0059

Phone: 414 248-4997

COMMENTARY 2

My impression before reading Nancy’s paper was that there was a substantial “learning curve” for the use of robotics and that Free Hand placement was very good in experienced surgeons hands.

How much time did the new technology take, was technical help necessary to run the equipment, did the equipment fail, was the final placement of the screws accurate, was there a higher infection rate because of the use of the technology, will the surgeon’s judgment be better because of the technology, or will his/her abilities be the same using the technology? In using navigation technology for brain surgery, I have found that the technology failed 1/3 of the time because of new people using it who were unfamiliar with it.

Her paper says just that. There is an impression being formed that robotic surgery will take over as a technology for spine surgery, which will make the manufacturers money. It is a new product from the manufacturer. They need to have new products. The learning curve is not important to them; that is the doctors’ problem, not theirs.

What you might want to consider is how many patients will be required to be successfully done using robotic technology to overcome the “learning curve”? Its’ complications should be counted as misplacement in the physician’s data and included in the reporting of results. For example, if a surgeon is doing a procedure and has 1 death, he/she needs to do 99 without any deaths to make the mortality rate 1%!

By “learning curve”, who plays the price? The patient. The reporting of complications can be questioned. For example, the interventionists only record complications for 24 hours! What about delayed rupture of an aneurysm, which I have seen, a week after the procedure, because of improper coiling. Isn’t that a complication? The “learning curve” complications in patients should be reported as complications, not as a “learning curve”.

How do people define complications? If the “learning curve” is used and discarded, or no complications are recorded after 24 hours, what does that mean compared to complication reporting as in the past. In previous times, all complications after the procedure, defined up to 30 days, were counted against the procedure or treatment. These complications would not have occured if the procedure was not done; so, they are all attributed to the choice of treatment.

I support new technology and ideas. But “compared to what?” is the question. There are ways to diminish the “learning curve” for new procedures. It is the physician’s responsibility to learn how to use the technology. This learning can be accomplished by practicing the new procedure in a laboratory, or morgue to diminish complications. Yes, that takes extra time and money, but that is what is best for the patient.

This is a different world. People are playing by different rules, their own rules to fit their agenda. That is not the actual TRUTH. But for some, truth does not matter. It is all about perception… and money.

James I. Ausman, MD. Ph.D.

Emeritus

Editor-In-Chief

Surgical Neurology International

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